The power adapter may be interfered by external factors during use. How can we solve this interference?
External interference generated by power adapter, such as harmonic current of power line, conducted interference of power line, electromagnetic radiation interference, can only be solved by reducing interference. On the one hand, it can enhance the design of input/output filter circuit, improve the performance of active power factor compensation (APFC) circuit, reduce the change rate of voltage and current of switches, rectifiers and freewheeling diodes, and adopt various soft switching circuit topology structures and control methods; On the other hand, strengthen the shielding effect of the enclosure, improve the gap leakage of the enclosure, and conduct good grounding treatment.
For external anti-interference capability, such as surge and lightning stroke, the lightning protection capability of AC input and DC output ports shall be optimized. The combination of zinc oxide varistor and gas discharge tube can be used to solve the lightning stroke. For electrostatic discharge, TVS tube and corresponding grounding protection shall be used to increase the distance between signal circuit and enclosure, or devices with anti-static interference shall be selected to solve the problem.
To reduce the internal interference of power adapter, we should start from the following aspects: pay attention to the single point grounding of digital circuit and analog circuit, and the single point grounding of large current circuit and small current, especially current and voltage sampling circuit, in order to reduce the common resistance interference and the influence of grounding ring; Pay attention to the spacing between adjacent lines and the nature of signals to avoid crosstalk; Reduce ground wire impedance; Reduce the area enclosed by high-voltage and large current lines, especially the primary side of transformer, switch tube and power filter capacitor circuit; Reduce the area enclosed by the output rectifier circuit, the freewheeling diode circuit and the DC filter circuit; Reduce the leakage inductance of transformer and the distributed capacitance of filter capacitor; Filter capacitors with high resonant frequency are used.
In terms of transmission channels, TUS with high anti-interference ability, high-frequency capacitors, ferrite beads and other components should be appropriately added to improve the anti-interference ability of small signal circuits; The small signal circuit close to the casing shall be properly insulated and withstand voltage; The radiator of power devices and electromagnetic shielding layer of main transformer shall be properly grounded; Large area grounding between control units shall be shielded by grounding plate; On the rectifier frame, the electromagnetic coupling between rectifiers and the layout of the ground wire of the whole machine shall be considered to improve the stability of the internal work of the power adapter.
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